Recording and reproduction of sound



April 26, 3932. T, MOREHOUSE 1,855,584

RECORDING AND REFRODUCTION OF SOUND Filed Dec. 6, 1928 & y 1 173. 2 2 4 5 &3.4

I VENTOR TE B. OREHO E A ORNEY sound to be recorded, or the light from a oon Patentecl Apr. 26, 1 932 V UNiTED STAT-Es TERRY BRYAN, MOREHOUSE, OF' eBook-tin, xiiiw fyoiu. AssIioRr'o mm c'or PORATION OF AMERICA, A CORPORATION OF a -In the usualprocess of the recording and reproduction of sound, iii-talking movi' -f p1ctures, the film has a sound record runningalong one edge between the edge of the picture `portion and thespr-ocket holes.

The sound record is usually photographically recorded either as varyinggdert light striturations or the Var-ying area" light and dark portions.- Thus the' sound-record" appears on the film as a strip h'avinga varying density'or having Variab'le area of light' and dark po'rtions so that a= light beampa'ssing through the' sound portion of the-film and focused upon a photo-'electrie ce'll causes' a fiuctu'ating current to -be produced` WlllCh current is utilized' t'ooperate convenient sound apparatus'. In the recording of thesound, either the light from a light source Variedin' intensity in accordance- Wll the' .stant light source shuttered by a Shutter Operating in' accordance" ;With Varying sound WaVes, is focused upon a'` moving* film 'and' serves to 'produce a`-`variahle density' record 5 or a varable'area record respectve'ly. Consderable 'diiculty 's experienced" n both' the recording and' the reproduction of sound bythe above methodsg-due to the fact' that in order to accurately reproduce the" rectly represent the actual acoustic displace-` ment of the diaphragm of the Inicrophone useduin' the recording. process; similarly in' the repro'ducton the reproducng apparatus" must be capable of integrating the' sound curve so 'that the current in the photo-eleotric cell'will corre'spond as exactly a's possible to the' instantaneous value of the sound record ed', and therefore' as nearly as possible to the" 'current in the' microphone circuit allowin of course, for the anphficaton characters'- ths-required. This is' all in` accordanc'e {With u the requirenent of acoustcs, that fo'r an-;ac

curate reproducton 'of sound it is necessary i that the 'reproducing appa'ratus'vbrate* not only at' the frequenoy of the nete being recorded'but' that theslope of the rpro ducer curve should be the-;sam at all times as the slope of the orgna'l acoustic: vilra-' tion.' This required' in' order' to give proper tmbre, resona'nce; ete-, to' the reprodu'ced tone aidfto' produce aithfully the various overtones and har'f''ic existing in'- the` original sound.` 'i

It is appa rent that with the presnt mm ods" of somd reprduction and rco'rdin if an appreciable area o A stant,' a Very sharp or suddei Siirge oftle'` acoustic dsplacenient will fail to act upo the light sensitive' cell and' prodiice' a? current of the proper proportion. the finite length' of the sound stripund'er inspection at a" given instant isi coniparativ elf greater than-the extent of thsddfl pue, the efiect of which is therforerouhddofi or summated I in r'eprod uctioj and th .t'j values are consequently ;mo'difid and, at*

high frequences e've lo'st altogetlier.

Further,-it'i`s evide'rit that` the resitance of" a' light sensitive cell hassoine' inertiaundr the rapid' changes of int'e'sity of the' light falling upon it and that this inertia wu'vary throughout* the range of light inten'sities. It is, 'therefore,' desirable' to' have s' nuch light strikngthe' cell at all'tinie's as ispossi ble. This has-been done means' of a'b'ia's ing light; the light'coniingfth'rough thefili' actn light;

Because of these" necessa'ry limitatios the presnt nethods n reproductionof sound from the photographic sound "record the tt'al 7 change of resistance ofadell uiidr"tli efiejct of lght from thel'ecordfis nessafily sniall and it'is there-fore diflicultttreproducefroh a single record a sound `Var'yng graty in volu'rne' 'or sound intensity' sound reproduced ifianuallyfl in* the' reprduc tion or to provide' aii additioilf or ven-ame; control record on thegame or a"'s-` rultaibus g merely asan ncrementto the biasing In designing photo-electric rproduing iting the amount of light falling upon the film or upon a photo-electric cell to a very small linear amount. This has been done by the use of a narrow'slit adapted to pass light *only to a small area of the film. It has also been done by the use of a'linear filament of tenuous formation and perhaps under tension, theimage of which'is focusedupon the film. The *light passing therethrough ;is caused to fall upon a photo electric cell and the resultant fluctuations serve to control the current in the reproducing apparatus. ;All

of these methods of reducing the linear eX- tent of llumnaton are sub ect to consider- I able" difficulty and many disadvantages.

Among these disadvantages are the possibility of the very narrow slitclogging and thus rendering ituselessfor either recording or reproductiom th'e difficulty in producing the proper amount of 'light from a very thin filamentor from a very thin slit in order to overcome the inertia efiects of the photo-electric cell and give asufiicient 'resistance change under light fluctuations and limited Volume range obtainable. r

` It is the main object of thisinvention to provide an improved means of sound recordt ing and reproduction.

It is another object of this invention to ob- .viate each of. the above noted difficultesas will be herenafter clearly set forth.

It isa further object of this invention to produce a light sensitive cell which will reproduce recorded sound inpulses from a film With great faithfulness and without undue distortion. v

Itis still a further object of this invention r to overcome the effects of the varying film density due to developng the film and permit sound to be reproduced from dierently developed films with identical results.

It is also an object of this invention to produce a method and light sensitive cell for the reproduction of photographic sound records which will give full range of sound or Volume intensity to `fulfill any of the requirements ofreproduction. j

It is another object of this invention to provide full automatic flexibility of Volume control in reproduction without the necessity of an additional or supplementary Volume control record.

It is another object of this invention to produce a method of sound reproduction wherein change in theflow of current in the reproducing system shall bedirectly proportional to the changes in the controlling intensity in recording.

V moving It is a final object of this invention to simplify the equipment necessary for the proper recordingl and reproduction of sound upon lms.

In carrying out this invention, the moving light sensitivefilm may be eXposed to a pencil of light, the lateral displacement of which is in direct proporton to the acoustic displacement of the sound being recorded. On

the positive print, the sound record Would then appear as a white line, the lateral displacement of whichis continuously varied. It is to be understood, of course, that the pencil of light would have a Very small longitudnal extent and might be in an elongated diamond shape, the length of which would be across the film. On, the other hand, the sound record may be made in the usual manner roducin what is known as asawtooth record, the use of which will ,be explained herei'nafter. i

Having briefiy described my invention reference should now be made to the accompanyng drawings which: V .fillu Fig. 1 shows a section of a talking movie m. v e i Fig. 2 shows a? schematic arrangement for a light sensitive cell constructed in accordance with my invention; v

. Fig. 3 is a schematic diagram showing the modification of the connections for reproducing sound in accordance withmy invention;

Fig. 4 is a schematic diagram showing a still further arrangement of my light sensitive cell: illustrating the .action in reproducing the ,record on the talking movie film;

Fig. 5 is an enlarged view of a section of i my light sensitive cell; 'Fig.f6 is an alternative method of reproducing from the film of my invention.

Referring now more particularly to the accompanyingdrawings Fig. 1 shows the sound record 10, disposed at the side 'of the ordinary movng picture film and consisting on the positive of'said film of an opaque sound strip 10 having a sinuous line representing tle sound fiuctuations traversing the length o it. i

The light sensitive cell shown in Fg. 2 is composed of two thin metallic plates 11 and 12, of high resistance material, separated a small amount, by a light sensitive substance 13. The plates ll and 12 have a very high' grammatically represented at 14. A li ht passing through the film isso focused t at its enlarged 'image will fall across the light sensitive cell and, the influence of light on the photo-electric material will form a conducting path .between the resistance plates 11 and 12 and the resistance of the cell .will be original film, becauserof the enlargement of the image thereof which is cast uponthe cell by any suitable focusing means.

Fig. 3 shows a similar arrangement wherein the Speaker element i's of a differential type and is adapted to be driven by circuits from either end of the light sensitive cell 16. The differentially actuating magnets 17 and 18 are connected to the opposite ends of the resistance plates 11 and`-12 and the resistance in circuit with each of said actuatingdevices is adapted to be difierentially varied by vary ing the location of the short crcuiting path between the plates 11 and 12 due to the Variation of the location of the image of light passing through the film of F ig. 1. y

Fig. 4: shows another arrangement wherein the plate 11 is similar to that of Figs. 1 and 2 and 'is composed of the high resistance material the resistance of which is consider-able with respect to the resistance of the light sensitive substance placed between the plates when the latter is under the influence `of light. The opposite or base plate19 is of any low resistance material so that the resistance in the crcuits of each of the Speaker' units 17 and 18 is adapted to be inversely varied in' accordance with the location of the beam of light thrown upon the cell through the fihnof Fig. l-with respect to the points' 21 and 22. g The device 17 has in its circuit, the 'high resistance between the points 21 and 23 and the' device 18 has in its circuit` the high resistance between the points 22 and 24. In this latter arrangement, the separation of the plates 11 and 19 by the light sensitive substance is unimp ortant.

It can be readily seen from this that the tone being produced is dependent merely upon the location of the single points 23 and 24 and in passing over apeak in the record these points will be successively moved to each and every point of the peak and the reproduction will consequently be considerably more faithful than it would be if a considerable portion of the linear length of thesound record had to be considered, as in each ofthe present processes.

Fig. 5 shows this principle more in detail as applied to the single drive, the thickness of the plate 11 in this case being considerably exaggerated. However, it is to be understood that the resistance of the ,light sensi.-` tive material is comparatively small when under the 'influence of light' of ,the desired intensity so that the resistance' of the path between the two plates. ll'and 19 is comparamember. r v

such as lamp black or india ink and thesan'dwich thus composed carefully cutofl` to pre V sent its cross section to the influence of.. ligh t. suitable connections arethen made and the cell is ready *f0r, operation. v v

- 'The `'cell may be con'striucted by placing a; platinun or tungsteno'r otherhigh resistance wire a short distance-:from another wire either of highor low' resistance and filling the` space between the two with any desired light sensi tive substance. i The wire' may: be supported in any des red manner,-as from an nsulatng iframe work or by securing to an: nsulatng A layerof light sensitive substance may be coated upon a piece of the plateand a line of some high resistance ic'onducting ink maybe painted or otherwise coated upon the surface of the .photo electric :substance and suitable connectionsmay be madethereto; In this; case withsthe light falliigupon the cell, can be` seen that' the portion of the resistance line on one side of the point where the shadow of the soundtrack cuts itwould determine the resistance of the cell. i i v i Aliquid reproducng cell 'may beus'ed in which 'case 'some light sensitive fluid suchas the potassium hydride is enclosed in the container and the plates 11 and 12 are comnosed of very fine' platinumor other high 'resistance wires separated by a small 'amountand sus= pendedwithin said fluid. A single high re sistance wire may beused instead of two and the connection made through: a ;Copper or other low resistance wire'. v e v Many otherequally obvious means may be employed, the only reqnirement of this invention being that the resistance' of the total cell is adapted'to be varied not bv a change of light intensity or amount of light in any sense but by the location of the beam of light imlens 31-` and the lens 35." Betweenthe film 32 and the cell 34:, -theulatter of which may' be.

of any desired Construction, is interposed a graduated light filteror' color screen 33. The screen 33 has a graduated density from side to; side, so that at one 'side a `considerable i amount of lightaimpinging-upon andpassing als through the film 32'nay pass to the cell 34: through the focusing lens 35, whereas, toward the other extremity; a different quantity of obvious 'thatit is 'necessary to ,confine the amount of'the film exposed to the light to a small' linear section 'as to-the usual method asto obtain faithful reproduction. However,

this method has the particular advantage that the actual density of the positive print of the film is absolutely unimportant because the density of the film can be compensated forby adjustng the streng'th of the. light 30. In

-developingfilm-it is hard to get'the proper density values and if these values' are directly converted into sound "values, considerabledifficulty may befmet with-'and the volume of` sound may vary from 'foot to foot of the film, Howevereven with varying' amounts 'of development a black portion of the negative will appear as a clear white line inthe posi-` tive print, and therefore the light falling upon the cell is dependent also upon the !at eral displacement of the clear part of thefilm. r

It is to be understood, of course, that with the light sensitive cell of myinvention'it is possible to use the ordinary saw tooth record and obtain the same results as mavbe obtained by use of thewhite line record. With the saw tooth records, there is used either the double cell element with' the connection from one end v removed or the single 'cell arranged in the proper direction. i

It is also' tobe clearly` und'erstoodthat a light sensitive cell of my Construction is" adapted to be utilized with any of the present' films 'in equally as eflicient a manner as the present photoelectric reproducing cells; It would therefore be unnecessary to change the type of cell in casean improper'film is being run. In the case however, that a variable density record is being run, the spacing of the plates 11 and 12 or 11-` and 19 is importantand is the determining integration' factor.

I Having thus described my nvention it is` to be unclerstood that I am not to be limited by the specific forms shown 'and described for the purpose of illustration'only but that other arrangements may be made within its scope which is to be determined solely by the appended claims.

Having now described my inventon, what I claim is: r i

1. The method of reproducti'on of sound from a moving film which comprises, converting the Varying lateral displacement of producing a beam' of light, varying the latp p rt a "through a moving soundrecord, and directly converting the lateral displacement of said beam into two inversely varying electric currents' i i i i 3. The method of reproduction of recordedsound from a moving film which comprises, producing a beam of light, varying the lateral displacement of said beam by passing it through amoving sound record, directly convertingthelateral displacement of said beam into-two inversely varying electric Currents, and clifierentially Operating a reproduoing unit by said electric Currents. i r 4:. The method or" reproducton of sound recorded upon a moving film, throughout the entredesired range of Volume, which comprises,'-produ'cing a-laterally varying beam of light, the lateral displacement of which will vary in direct proporton to the amplitude of the acoustic displacement to be repro'duced, and the frequency of whose lateral displac ement will correspond to the tone to be reproduced, optically amplifying the lat- 'eral displacement of-'said'beam, converting said later al displacement into two inversely varying electric Currents, the intensity of each of which are varied at the tone frequency by 'an amount directly and indirectly respectively, to the desired acoustic displacement, and actuatng a differentially operated loud speaking unit by said'currents; I

5. Apparatus for the reproduction of talking movies which comprises', a photographic sound 'record adapted to be continuously moved, a light source, and a light sensitive cell, said light source, film, and light sensitve cell' being so arranged that an enlarged image of the sound portion of said film is cast upon the light sensitive cell, and said light sensitive cell being composed of means imageof said sound portion will cause a current to vary in accordance with said lateral displacem'ent of the limit of said image.

6. Apparatus for the reproduction of talking movies which comprises a photographic sound record adapted ,to be continuously moved, a light source, and a light sensitive cell, said light source, film,' and light sensitive cell being so arranged that an enlarged image of the sound portion of said film is cast upon the light sensitive cell, and said light sensitive cell'being composed of means whereby the lateral displacement of the image of said sound portion will cause a current tofivary in accordance with the lateral displacement of onelmit of said image and second current to vary inversely in accordance with' the lateral d'splacement of the other limitofsaid image.

7. Apparatus for the reproduction of talking movies which com prises, a 'photographic sound 'record adapted to be continuously moved, a light source, a light sensitive cell, said light source, film, and light sensitive cell being so arranged that an enlarged image of the sound portion of said film is cast upon the light sensitive cell, and said light sensitive cell being composed of means whereby the lateral displacement of the image of said sound portion will cause a current to vary in accordance with the lateral displacement of said image and second eurrent to vary inversely also in accordance with the lateral displacement of said image and means for causing said varying electrical currents to operate difi'erentially upon an acoustie member to reproduce the sounds recorded upon said film. e

8. The method ,of reproduction of sound from a moving film which comprises converting the varying lateral displacement of the edges of a beam of light into two inversely varyng electric Currents.

9. The method of reproduction from a movi ing film which comprises converting the lateral displacement of the two edges of a bea-m of light into two inversely varyng electric currents and differentially actuating a reproducing unit thereby.

10. The method of reproduction of recorded sound from a movng film which comprises producing a beam of light, varyng the lateral displacement of said beam by passing it through a moving sound record, and con- Verting the lateral displacement of the edges of said beam into two inversely varyng electric Currents.

11. Means for converting the lateral dsi placement of a beam of light into sound, including a light sensitive cell, means for moving said b eam across said cell, a diaphragm and a pair of coils connected to said cell for Operating said diaphragm differentially in accordance with the position of said beam on said cell.

TERRY B. MOREHOUSE. 

